There is a variety of fabrics (different materials and weaves) designed specifically for that purpose. They hold up to UV and wind, dry quickly, are resistant to abrading through where they are secured or in contact with supports, and offer different levels of light filtering. They are sold as "outdoor canopy fabric" and "awning and shade ...
If you want a cheap option, second hand tents and tent-like tarps.
New tarps are available but those will be expensive if you only want to use them as fabric.
Sails of smaller boats or surfboards can also be used.